[Loanshark]

I just picked it up today... I did check the compression, they were 80 psi each. Is this low? Could this be causing the cold start issue? It runs good and starts fine while warm.

The P.O. Said he adds one ounce of oil per gallon of gas, in addition to the oil injector... I plan to block it off and premix. What should I be checking on?

Any help/ advice would be greatly appreciated!!!

 

[Loanshark]

I sure could use some input on this thing... I took it to the lake today and had a heck of a time getting it to run. It would fire a couple hits every now and then, then nothing. Almost killed the battery, and probably the starter.

I pulled the plugs (soaked) and changed them. It fired up and stayed running for about 30 minutes. Long enough for my wife to get away from the dock then it died "abruptly" according to her. She re-started it several times but it only ran for a few minutes a time, then finally it wouldn't start anymore. The previous 4 trips to the lake have been flawless. I took my gps on the last trip and noticed it toped out around 34mph. Everything I read so far tells me thats the normal top speed for these. I'm around 300lbs so I took that as an indicator that everything is A-OK.

I'm still curious about my compression numbers, most seem to be getting higher numbers than mine... I figured it was fine after how well it's been running. I'm getting spark, now what? Rebuild the carb? Top end rebuild? Complete rebuild? New engine? New waverunner? Please help.

 

[Loanshark]

Any little bit of info could be a help, please don't be shy...

 

[Ernest T]

Man 80 psi on both cylinders is WAY low. No wonder you are having problems getting it to run. Generally, 2 cylinder 2 strokes should have around 140 psi, and 3 cylinder 2 strokes around 110 psi per cylinder. There also should be no more than a 10% difference between cylinders.

Time for a top end rebuild.

 

[Loanshark]

Thanks for the reply Ernest T, you are a helpful dude. I wonder if you know how likely it is to need bored out. Are any special tools needed to do a top end rebuild? If I do all the work myself what is it likely to cost me?

Don't mean to be pushy, but it seems like you might be the right guy to ask...

Thanks again!

 

[Ernest T]

I've rebuilt motorcycle engines, but never a PWC.......I'm guessing the process is similar. You can get the whole top end kit including pistons and cylinders for under $300 from SBT with their exchange program, or I think you can get the complete engine for $500- $600. Personally, I would recommend using a kit like SBTs with the pistons and cylinders rather than trying to bore out the cylinders.............cost would be similar I'd say, but the kit would be easier. Also, it seems like I read someplace that the Yamaha cylinders can't be bored due to the plating.

As far as special tools, its hard to say without knowing what you have. Things like gear/wheel pullers, piston ring tools, torque wrenches, etc. can usually be borrowed/rented from your local auto parts store. At my local store, if you need a tool, you pay for it up front, but they will fully refund your money when you bring it back as long as its not damaged........works good for rare tools that you use only once.

My advice would be to call the guys at SBT. They could tell you exactly what you will need.